Under certain circumstances the desired destination for an air vehicle lacks a suitable runway. In these situations an air vehicle capable of vertical or very short landing would be an advantage.
Helicopters are capable of vertical take-off and landing. Helicopters use rotary wings powered by an engine through a gearbox. This results in a complex system limiting useful load, and range and increasing costs when compared to a fixed wing airplane.
A helicopter powers its rotor from an engine whereas an auto-gyro spins its rotors by an external upward airflow passing through the rotor. This can be achieved by either forward flight with the rotors tilted backwards using a separate propulsion unit or by non-powered almost vertical descent that leads to a gentle landing.
The helicopter and auto-gyro have a limited maximum forward speed due to the asymmetric lift between a retreating blade and an advancing blade. A rotor also generates high aerodynamic drag as compared to an equivalent fixed wing aircraft.
An air vehicle that combines the advantages of a fixed wing for cruise with a rotary wing for landing provides an efficient means of air transport for the following (but not limited to) types of aircraft:    I. A military cargo glider where after landing it is discarded.    II. A Navy carrier aircraft where (especially when unmanned) a gentle landing is required but could be reconfigured to take-off using the catapult system.
The Herrick convertible aircraft comprised an upper wing on top of a mast that was locked into position during cruise and when combined with the lower wing operated as a biplane. When the wing was unlocked the top wing was free to rotate as an auto-gyro, reference U.S. Pat. No. 2,699,299.
The rotor was initially powered by rubber bungee cords contained inside each upper wing half, running through an aluminum tube. Prior to take-off, two people rotated the wing twice in the opposite direction to the auto-rotation. The upper wing was then locked in the biplane cantilever wing position. When the pilot released lock during the flight, the bungee cords rotated the wing spun twice at 60 revolutions per minute. The now-spinning wing rotated freely and increased its speed to 220 revolutions per minute in auto-rotation.
This type of approach requires the airflow over one half of the wing being reversed during rotation. To accommodate this bi-directional airflow, the wing section shape is bi-convex or somewhat lenticular. This shape is widely used for supersonic aircraft and missiles but grossly inefficient when used at subsonic speeds.
The following invention allows fixed wing to convert to auto gyrating wings but without the disadvantages of using bi-convex wing shapes.